The present invention concerns a process and a device for the manufacture of posts of concrete or the like, of polygonal cross section.
It is known that the preparation of concrete structural elements involves the use of forms of wood or metal in which the concrete is poured and where it is left to harden. These forms are expensive and heavy and difficult to handle. Furthermore, on the worksites the operations of setting and stripping forms are often difficult.
In the case of simple pieces such as posts, it has already been proposed to cast the concrete in simple cardboard sheaths. The tests performed for posts of circular section have proven perfectly satisfactory, and this process is now employed in the art. It offers the advantage of being very easy to employ and of being much less expensive than the ordinary methods using complex forms.
Despite these advantages, it has not been possible, however, to apply this process to the production of posts of polygonal (square, rectangular or other) cross section, for in every case the cardboard sheath used deforms by sagging to assume a circular or rounded section.
To remedy this problem, it has been proposed, in FR-A-1 453 489, to make use of a cardboard form of polygonal section, which is reinforced by applying boards to its external faces, these boards being held in position against the faces of the form with the aid of clamps.
GB-A-648,809 has also proposed using for this purpose a form of polygonal section constituted by a plaster panel gripped between two carboard boards, this panel having parallel folding lines enabling it to be folded to form a liner which is externally sheathed in a protective sheet of paper, fabric, leather etc.
All these processes, however, are expensive and difficult to employ.
The present invention aims to remedy this problem by proposing a process for making concrete posts of polygonal cross section that will be as easy to employ as the cardboard sheath process used for the manufacture of posts of circular section, that will not be more expensive than the latter, and which will use, for the pouring of the concrete and for setting it, not a wooden form but a simple liner which does not deform.